Ultrahigh speed optical coherence tomography for ophthalmic imaging applications

Abstract

Optical coherence tomography (OCT) is a non-contact, non-invasive, micron-scale optical imaging technology that has become a standard clinical tool in ophthalmology. Fourier domain OCT detection methods have enabled higher sensitivity and imaging speeds compared to previous generation timedomain OCT. Spectral / Fourier domain OCT (SD-OCT) detects the interference spectrum using a broadband light source and spectrometer. Swept-source / Fourier domain OCT (SS-OCT) detects the interference spectrum over time using a wavelength-swept laser. Current standard commercial ophthalmic clinical systems based on SD-OCT technology have imaging speeds of 20,000 - 40,000 axial scans per second and axial resolutions of 5 - 7 ptm. In this thesis, ultrahigh speed OCT for ophthalmic imaging applications are presented. SD-OCT systems using high speed CMOS camera technology can achieve imaging speeds over 70,000 axial scans per second. Axial resolutions better than 3 ptm can be achieved with multiplexed broadband superluminescent diodes. A novel registration motion-correction algorithm for volumetric OCT datasets reducing motion artifacts and improving signal quality is investigated. Ultrahigh speed, ultrahigh resolution SD-OCT ophthalmic imaging applications including small animal retinal imaging and clinical imaging of age-related macular degeneration (AMD) are illustrated. SS-OCT systems using short cavity wavelength-swept laser light sources can achieve imaging speeds over 100,000 axial scans per second with 6 pm axial resolution for small animal and clinical imaging. The high sensitivity of SS-OCT enables enhanced vitreous imaging, visualizing features in the vitreous and vitreoretinal interface. Finally, a new vertical cavity surface-emitting (VCSEL) technology based wavelength-swept laser light source SS-OCT system with tunable speed and wavelength range as well as long coherence length enabling ultrahigh speed and ultralong range OCT imaging applications is demonstrated. In addition to comprehensive structural imaging, the emergence of functional OCT imaging of retinal blood flow using ultrahigh speed OCT may also improve the understanding of ocular disease pathogenesis. Therefore, ultrahigh speed OCT is a promising tool for the diagnosis and management of diseases in ophthalmology.